The present invention relates to a device for supporting threaded spindles in order to prevent a sag thereof due to a dead weight of the spindle, and/or sag which would arise from a nut segment engaging into the spindle from above. The supporting elements of the invention are largely maintenance free, self-seeking, and support the spindle on rollers so that no sliding friction occurs.
The problem often exists in machines in electronic reproduction technology, machine tools, adjustment devices, and the like that high-precision spindles must be seated in self-bearing fashion over great lengths. As a consequence of the dead weight of the spindles, a sag between the bearing points thereby arises, this sag resulting in the required precision being in doubt in many cases. There are many applications (for example given threaded spindles for conveying machine tool carriages, etc.) in which for delivering longitudinal motion to the carriage, a nut segment can engage (through a spring force if needed) with threads of the spindle proceeding from above. Of course, resilient devices again increase the sag of the free spindle and thus increase the imprecision.
German AS No. 1 243 496, incorporated herein by reference, discloses a fixed stay for processing cylindrical workpieces wherein the workpiece is supported by means of rollers. Although the roller blocks in which the rollers are seated are tiltable around a shaft lying parallel to the workpiece axis so that they are self-seeking in the plane orthogonal to the workpiece axis, they are not self-adjusting in the plane perpendicular thereto, so that small errors in parallelism of the roller axes are not compensated. Furthermore, none of the rollers is movable on all sides around the center of its body, so that the rollers could automatically compensate a lack of parallelism with respect to their own running shafts. The rollers are thus not compelled to find a line contact against the rotational member to be supported.
The German utility model No. 69 22 062, incorporated herein by reference, discloses a roller bearing for conveyor spindles. However, the publication is predominantly related to roller elements which replace the use of a nut segment. Although support elements for the spindles with rollers are mentioned, they are not disclosed in detail.
German utility model No. 81 17 878.6, incorporated herein by reference, discloses a spindle support for threaded spindles which are extremely thin. The spindles are free-turned to a diameter less than a diameter of their threaded core at the locations at which the support bearings act. In order to bridge these irregularities, the nut segment is designed sufficiently long such that it covers the free-turned locations. In addition to plain bearing half-liners, rollers as supporting elements are also mentioned here, but their design is not disclosed in greater detail.
None of the known devices show roller supporting elements which automatically find a line contact when placed on the spindle.